Design and application of universal adjustable fix

2022-08-21
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Design and application of universal adjustable fixture for drilling transmission shift shaft (II)

(1) universal matrix

drilling template is firmly connected with the body through locating pin, equipped with drilling, reaming, drilling template three holes and installing bushing to ensure that the hole is 0.02 mm to the center of V-shaped block

drilling three holes of the template is used to expand the drilling position and clamping space of different products. This method ensures that the key components of the fixture have the rigidity, accuracy and service life similar to the special fixture

(2) composite adjusting elements (V-shaped block, baffle, positioning block)

two different specifications of V-shaped blocks (suitable for shaft diameters below d16.3 and above D22) are connected with the T-shaped groove of the body through the positioning key, and sliding with the positioning block through the concave groove, and tightly connected with the baffle to form a composite adjusting element. The positioning error of this combined method is relatively small, and in the actual machining process, the clamping force and cutting force of the workpiece can offset each other, which can reduce the displacement error between components after being forced

during installation and adjustment, move the V-shaped block to ensure the distance between the concave groove center and the drilling template, or adjust the baffle set screw to ensure the distance between the shaft end face and the drilling template

(3) angle plate

installation method: select the angle plate and orientation plate according to the requirements of workpiece positioning angle, and connect them with the positioning block and orientation plate through the orientation key

working principle: slide or fix the orientation plate on the angle plate through the orientation key to ensure the angle requirements of the workpiece positioning groove or hole. Achieve positioning angle

(4) straight plate orientation plate

installation method: according to the positioning requirements of the workpiece groove or hole, select the positioning shaft or positioning column, and connect it with the positioning block or angle plate through the orientation key

working principle: fix or slide on the positioning block or angle plate through the directional plate to position the workpiece slot or hole. When positioning the groove, select the positioning column to meet seven positioning requirements; When positioning the hole, select the positioning axis to meet three positioning requirements

5. 11 fixture positioning modes

according to the different process positioning requirements of the workpiece, the ideal fixture mode can be achieved by changing the fixture angle plate and positioning block and moving the V-shaped block and pressing plate position. The fixture positioning mechanism can realize 11 positioning modes

(1) workpiece axial end face positioning (see Figure 7)

Figure 7 workpiece axial end face positioning

move the V-block and fine tune the baffle screw to ensure the distance from the shaft end face to the center of the drilling template hole. This positioning method is applicable to drilling the first non included angle hole

(2) horizontal positioning of workpiece groove (see Figure 8)

horizontal positioning of workpiece groove in Figure 8

move the V-shaped block to ensure the distance between the workpiece groove (or hole) and the center of the drilling template hole, and then push the positioning block to make the positioning pin closely contact with the workpiece groove (or hole), so as to realize the corresponding angle of drilling. It includes four positioning modes: upper positioning, lower positioning, angle positioning and hole positioning

(3) workpiece groove vertical positioning (see Figure 9)

Figure 9 workpiece groove vertical positioning

the method is the same as above, including six positioning methods of workpiece groove right side positioning, left side positioning, angle positioning, vertical hole positioning and angle hole positioning

6. Fixture installation and adjustment process

see Figure 10 for fixture installation and adjustment process

Figure 10 fixture installation and adjustment process

fixture accuracy analysis

1 Take the 2-5 + 0.08 hole drilled on the first and second shift fork shaft of 205d transmission as an example. See Figure 11 for the process guidance

Figure 11 process guidance figure

2 Fixture error analysis

take drill hole 2 as an example to analyze the hole spacing, perpendicularity, symmetry and included angle errors

(1) fixture manufacturing error (Manufacturing)

the manufacturing deviation from the center of the drill sleeve to the center of the V-shaped block is 0.02mm, and the parallelism between the theoretical axis of the V-shaped block and the positioning datum plane of the body is 0.02mm; 10 angle plate angle manufacturing error is 2. That is, the center of the drill sleeve is in the radial direction of the workpiece axis: manufacturing =0.01mm; The center of the drill sleeve is in the vertical direction of the workpiece axis; Manufacturing =16.3 0.02 271=0.0012mm (shaft section); Included angle between the center of the drill sleeve and the shaft groove of the workpiece shaft: manufacturing =2

(2) fixture installation error (installation)

during fixture installation, the calibration pin is introduced into the fixture by the drill press jacket, and the drill sleeve aligns the workpiece. The maximum offset between the center of the calibration pin and the center of the drill sleeve is the fixture installation error. The manufacturing deviation of the calibration pin diameter is 4.995 ~ 4.988mm, the drill sleeve is selected with the factory standard, and the manufacturing deviation of the inner hole is 5.01 ~ 5.027mm; Axial installation error of composite adjusting element is 0.02 mm; 10. The comprehensive installation error of the angle plate is about 2, that is, the center of the drill sleeve is in the radial direction of the workpiece shaft: installation =0.0195mm; The center of the drill sleeve is in the axial direction of the workpiece shaft: installation =0.02mm; Included angle between the center of the drill sleeve and the shaft groove of the workpiece shaft: installation =2

(3) workpiece positioning error (positioning)

the V-block positioning reference coincides with the process reference; The positioning error caused by the external control of the motor rotation of the tensile testing machine for workpiece straightness steel wire data is very small; There is no gap between the positioning pin and the workpiece slot, so the positioning error is zero. The UK will definitely regard graphene as one of the four emerging technologies to be developed in the future, that is, positioning =0. (4) Guide error (Guide)

the error formed by the gap between the drill sleeve and the drill bit. The drill bit D5 adopts the GB standard, as shown in Figure 12. The diameter manufacturing deviation is 4.982 mm ~ 5.0mm, and the maximum gap between the drill sleeve and the drill bit is 0.045mm, that is, the drill bit center is in the radial direction of the workpiece axis: guide =0.045 (15+5+ 16.62) (152) =0.0422mm; The drill center is in the vertical direction of the workpiece axis: guide =16.3 0.045/15=0.049mm (in the shaft section); The included angle between the drill center and the shaft groove of the workpiece shaft: guide =tg-1 (0.045/15) =10.3 (in the shaft section)

Figure 12 guide error diagram

(5) machining error machining

the dimensional accuracy of the machined hole itself is the aperture deviation, and its axis position accuracy is affected by the relevant accuracy of the fixture, machining =0

the total deviation obtained from the above analysis: hole pair degree error (manufacturing + positioning + guiding + processing) 2= (0.01 + 0.0422) 2=0.1044mm; Hole perpendicularity error: manufacturing + positioning + guiding + processing =0.0012+0.049=0.0502 mm; Hole spacing error: manufacturing + positioning + guiding + processing + installation =0.02+0.0422=0.0622 mm; Hole angle error: manufacturing + positioning + guiding + processing =2 +10.3 =12.3

in the above analysis, the center distance deviation on the fixture is taken as two-way system. In the total deviation calculation, the guide error is lower than the fixture installation error, so the guide error is taken, so the limit size of the workpiece is: hole distance 162 0.062mm, symmetry 0.104mm, perpendicularity 0.05mm, and the included angle between the hole and the shaft groove 8012.3. The above error caused by the fixture is basically within the allowable tolerance range of the workpiece. Although the symmetry is slightly out of tolerance, it has been proved by the use of the copper strip tension tester for cables produced in Jinan period that it meets the standard gb/t 11091 ⑵ 005. The possibility of occurrence is very small and can fully meet the requirements of process accuracy

technical and economic effects of universal adjustable fixture

conclusion

as one of the modern machine tool fixtures, the general adjustable fixture rose at the end of the 20th century. At present, the application of the general adjustable fixture in the automotive parts manufacturing industry has been paid more and more attention and promoted

the shapes of automobile transmission box and miscellaneous parts are different, and a certain part often needs to be equipped with dozens of special fixtures and inspection fixtures. In the current fierce market competition environment, when manufacturing enterprises face a large number of passive situations such as tooling design, manufacturing waiting and rapid elimination in multi variety, medium and small batch production, the general adjustable fixture reflects a better market response ability

practice has proved that we have lost the product image and market design of this set of fixtures. After being put into use together with the milling slot universal adjustable fixture designed at the same time, it greatly improves the adaptability of the workshop site, improves the chaos of the production site, is deeply welcomed by operators and workshop managers, and realizes the design goal of flexible and universal special fixtures. It is a fixture design scheme worthy of wide promotion and application

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